1. Field of the Invention
The present invention relates to an air supply device, wheel, and a tire unit.
2. Related Art
Automobiles, bicycles, or the like are driven by rotating tires, and air pressure in the tires must be always kept in a predetermined range for safe traveling.
However, there is a problem that since air pressure in a tire is decreased with passing of time and during traveling, it is necessary to supply an air into a tire in manual operation by means of a compressor or the like and so control of air pressure in a tire takes time and labor.
In order to solve such problem, a tire pressure control system (device) has been conventionally proposed in, for example, JP-A-H07-69017.
However, the conventional device is disadvantageous in that it is complex in construction, becomes large-scaled in system, and needs a complex control for driving the device, and a battery or the like of a vehicle side is necessary as an energy source for driving the device.
An object of the invention is to provide an air supply device, which is simple in construction and can automatically and surely supply air into an air filling portion of a rotating body without the use of any energy source (for example, sources of electricity, fuel, high pressure, or the like), a wheel, and a tire unit.